Monday, August 06, 2012

Pleasant week ahead..

Generally dry and warm weather is expected through the upcoming week with little in the way of weather systems affecting Winnipeg and the Red River valley. Models are indicating a weak system tracking from southern Saskatchewan into North Dakota Tuesday night into Wednesday that may bring some scattered showers and thunderstorms over southwest MB, but the bulk of precipitation with that system is expected to remain south of the border. Other than that, it looks like mainly sunny and seasonably warm weather this week with temperatures in the mid to upper 20s, along with comfortable humidity levels and generally light winds. Enjoy!

Anonymous.. the 8-14 day CPC outlook does indicate a change to below normal temps over western Prairies and above normal precip over us, which is the first guidance I've seen in awhile showing below normal temps over the west. They note confidence is low due to poor model agreement, which in itself may be signalling the beginning of a pattern change. ECMWF is one of the better models for medium to long range forecasts, so it does lead to the possibility of a change to a cooler pattern for us next week. Hope not.. I'm not ready to give up on this great summer weather yet!

So this would be probably mean that the severe weather threats for us will be diminishing with the cooler weather not that there ever was a true severe weather season this summer at least here in Southern Manitoba.

Speaking of thunderstorms, I see the threat of some rain on Saturday, does that also bring a chance of thunderstorms as well?

Yes, severe thunderstorm threat will diminish with cooler weather, but our severe weather threat diminishes fairly quickly once you get into August anyways. You can still get some good storms, but overall, dynamics tend to be weaker, and moisture levels are lower as crops mature and get harvested, and surface moisture generally dries up. Solar strength starts to weaken as well, which tends to limit heating as well as lift to initiate convection. So overall, we're in a declining phase as far as a severe weather threat goes. But it's not over. We've had severe storms with hail and tornadoes well into late August and even early September given the right setup.

Some of the best thunderstorms I can remember were in August. Particularly August 8, 1993 when Winnipeg got 70mm of rain. Another one on August 27, 2003 when we had 50mm of rain from thunderstorms lasting many hours that evening and again in August 2004 when we got some good storms, ones that lasted several hours. Those are always my favorite, the ones that go on for longer then an hour (last all day or all evening into overnight), which I can't remember the last time has happened!

Rob, What kind of conditions do you need to have in place to receive thunderstorms for a few hours or more especially in Winnipeg? We need the rain, and storms to satisfy the weather enthusiasts like us.

Note that elevated convection can persist well into the fall. Severe and strong storms with hail and torrential rain have occurred well into October and even November in recent times. The key is a strong LLJ overriding a warm front just to our south... particularly when the pattern stalls. Deeper into the fall season, usually a large, dynamic system is needed to tap enough warmth and moisture out ahead of the disturbance from the Gulf.

Interesting article in the Ottawa citizen regarding problems with EC's observing network.. specifically with the inability to properly archive climate info from autostations now deployed by NavCanada at Canadian airports. Daily and monthly climate data at several major sites, including Ottawa, has been missing for 8 months now. While I can understand that there might be some data compatibility issues with a new monitoring system, I'm puzzled why it takes more than 8 months to fix the problem.

CPC continuing to hint at below normal temperatures and above normal precipitation for Southern Manitoba over their short term outlooks (6-10 and 8-14 days). Seems like a pattern shift may be on the way.

Yeah, ECMWF/GFS now hinting at a major cool down this time next week behind another rather unseasonably strong system, with 850 mb temperatures only near 0 to 5°C behind the system. It could change a bit of course, but wow this would be quite the cool down if it occurs. And those cold temps would likely only last a day or a couple if it occurs.

Yikes, the GFS paints an ugly picture late next week into the weekend next week. Under its scenario, it could get very cold for this time of year with night temperatures dropping to close to the freezing mark. Could definitely spell some lake-effect rainfall if we get some strong northerly winds.

It's still quite early though thankfully! Hopefully it's over reacting!

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